The re-use of existing and official data has a very long and largely honourable history in education and social science. The principal change in the sixty years since the first issue of the British Journal of Educational Studies has been the increasing range, availability, and quality of existing numeric datasets. New and valuable fields of endeavour have formed around specific applications of these datasets, and some promising analytical techniques have been devised to deal with them. At the same time, the opportunities provided by these datasets have thrown up fascinating methodological and other challenges. This paper presents a brief summary of all of these developments, with illustrative examples. The paper then considers two fields of...